Ovarian response to gonadotrophin releasing hormone in non-cyclic goats

Abstract

The study was conducted to evaluate the effect of Gonadotropic Releasing Hormone (GnRH) on ovarian activity and its usefulness in restoring normal oestrous cycle in adult non-cyclic goats. A total of 60 healthy Malabari, Malabari x Saanen and Malabari x Alpine does aged one to four years, with a record of one or more kiddings and 45 days post partum belonging to Goat Farm of Kerala Agricultural University, Mannuthy were closely observed for a period of 60 days for the occurrence of oestrus and serum samples were collected at fortnightly intervals for the estimation of macro and micro minerals. Serum progesterone profile in eight cyclic and sixteen non-cyclic does, selected at random, were estimated by Radioimmunoassay using a coat-A-count progesterone kit. Out of eight non-cyclic does treated with potent GnRH anologue (Buserelin) three responded to single dose and one responded to a second dose. The oestrus was exhibited at a mean of 87.000 ± 9.950 h after the administration of GnRH analogue. The mean length of oestrous cycle and duration of oestrus in cyclic does were 20.313 ± 1.553 days and 37.500 ± 7.263 hrs while in GnRH responded does were 12.750 ± 0.830 days and 18.000 ± 4.240 hrs, respectively. The mean serum phosphorus level was found significantly higher in GnRH responded does (5.375 ± 0.205 mg per cent) as compared to cyclic does (4.800 ± 0.260 mg per cent) and non-cyclic does (4.770 ± 0.280 mg per cent). There was significantly higher serum copper level in GnRH responded (1.123 ± 0.089 ppm) and in cyclic does (1.160 ± 0.170 ppm) as compared to non-cyclic controls (0.830 ± 0.110 ppm) . The serum zinc level was significantly higher in non-cyclic (1.510 ± 0.430 ppm) as compared to cyclic (1.180 ± 0.120 ppm) and GnRH responded does (1.155 ± 0.091 ppm). There was no significant difference in the serum calcium, cobalt and manganese level between the three groups. The mean serum progesterone in cyclic does for the two consecutive cycles was 0.304 ± 0.087, 1.294 ± 0.382, 2.531 ± 0.758, 3.619 ± 0.794, 2.456 ± 0.430 and 0.871 ± 0.246 ng/ml and in GnRH responded does was 0.158 ± 0.026, 0.800 ± 0.177, 1.475 ± 0.334, 0.675 ± 0.236, 0.280 ± 0.030 and 0.120 ± 0.021 ng/ml on day one, four, six, ten, 14 and 18 of cycle, respectively. The overall mean serum progesterone during induced cycle in GnRH responded does was 0.535 ± 0.139 ng/ml which was significantly lower as compared to cyclic does (1.848 ± 0.339 ng/ml) but significantly higher as compared to untreated non-cyclic does (0.190 ± 0.106 ng/ml), Detailed biometry studies of pituitary ovary, uterus and cervix of GnRH responded does showed non-significant increase in the size and weight as compared to untreated non-cyclic does. The mean number and size of follicles were found significantly higher in GnRH responded as compared to non-cyclic does. The mean tissue ACP, ALP and LDH in the pituitary, ovary and uterus of GnRH responded does showed non significant increase as compared to untreated non-cyclic does. The mean LDH level in both ovaries together was significantly higher in GnRH responded does as compared to non-cyclic does. The present study confirms that GnRH administration in non-cyclic does has reactivated the ovary by increased follicular growth, maturation and corpus luteum formation. However, the length of induced oestrous cycle, duration and intensity of oestrus was significantly less in GnRH responded does